Integrated circuit devices, such as semiconductor chips, are commonly packaged using a lead frame and encapsulant. For example, one or more semiconductor chips may be physically attached and electrically connected to a lead frame. The encapsulant covers the lead frame, semiconductor chip and electrical connections. The lead frame includes external electrical terminals that allow the semiconductor chip to be electrically connected to a printed circuit board, for example. This packaging arrangement allows for an electrical connection between the semiconductor chips and other devices to be effectuated while simultaneously protecting the semiconductor chip and electrical connections from damaging environmental conditions, such as moisture, temperature, foreign particles, etc.
Many semiconductor processing techniques utilize lead frame strips to simultaneously process a number of semiconductor devices. A lead frame strip includes a number of unit lead frames connected to one another. Each unit lead frame provides the lead construction for a single packaged device. One or more semiconductor dies can be affixed to and electrically connected with each unit lead frame. Subsequently, a molding process can be applied to the lead frame strip to encapsulate each of the semiconductor dies. Eventually, the unit lead frames are singulated from one another to form individual packaged devices. Thus, the lead frame strips allows for parallel processing steps that increase the throughput and reduce the expense of semiconductor manufacturing processes.
There are a variety of molding techniques that may be utilized to simultaneously encapsulate a number of semiconductor dies on a lead frame strip. For instance, a transfer molding process may be performed. In a transfer molding process, the encapsulant structure is formed by a liquefied encapsulant material, such as a thermoset resin or an epoxy. The liquefied encapsulant material is injected into a cavity that surrounds the semiconductor die (or dies) on each unit lead frame. The liquefied encapsulant material is then hardened into a solid state and the cavity mold structure is removed.
One limiting factor in every transfer molding process is the number of molding cavities that the molding tool has to accommodate individual semiconductor dies from the lead frame strips. Increasing the number of molding cavities typically requires an increase in the size of the molding tool, which in turn increases the cost of the molding process. Another limiting factor in every transfer molding process is the amount of time required to harden the liquefied encapsulant material for a given batch of unit lead frames. It is therefore desirable to increase the throughput of transfer molding processes by increasing the number of unit lead frames that can be molded in a given amount of time.